6.2 Nitrogen compounds, polymers and synthesis.

Question 1

What are amines?

Answer 1

Any derivative if ammonia.

Primary amine: NH2 attached to one carbon chains.

Secondary amine: NH attached to 2 carbon chains.

Tertiary amine: N attached to 3 carbons.

Question 2

List some of the uses of amines.

Answer 2

They occur naturally in the body as neurotransmitters and hormones:
e.g serotonin

They are used for many drugs:
e.g pseudoephedrine

Question 3

Describe the reaction of amines with an acid.

Answer 3

Amines are basic as the lone pair on the nitrogen accepts a proton.

Accepting a H+ ion forms a quaternary ammonium ion.

Therefore reacting with an acid forms a salt.

e.g
CH3NH2 + HCl = CH3NH3+ Cl-

Question 4

Explain how a primary amine is formed using a haloalkane

Answer 4

Haloalkane reacts with excess ethanolic ammonia.

Nucleophilic substitution: Halogen is substituted with amine group.

R-X + 2NH3 –>

Question 5

Optical isomerism.

Answer 5

This occurs in molecules with a chiral centre.

The chiral atom is attached to four different atoms.

This forms two non-superimposable mirror images.

Each isomer can react different. E.g in drugs, an isomer of thalidomide can cause birth defects

Question 6

Why is it important to only synthesise one type of optical isomer in pharmaceuticals? (4)

Answer 6

Two different isomers may have two different activities in the body.

One isomer may not be active.

An isomer may have harmful side effects.

Saves costs when products are being separated.

Question 7

How can a nitrile be formed from a carbonyl?

Answer 7

Carbonyl + HCN (formed in situ from NaCN and H2SO4)

Undergoes nucleophilic substitution mechanism.

Question 8

Describe the two ways of reducing nitriles.

Answer 8

1. Reaction with Hydrogen
   Catalyst: nickel
   Reduction reaction.
2. Reaction with LiAlH4
   Nucleophilic substitution mechanism.

Question 9

Describe acid hydrolysis of nitriles. (3)

Answer 9

Nitrile + dilute acid (e.g HCl)

Under reflux

Forms carboxylic acid and Ammonium salt

Question 10

Describe the preparation of nitrobenzene from benzene. (2 steps)
Name each type of reaction that occurs.

Answer 10

1. Benzene to nitrobenzene:
   - Benzene is reacted with conc HNO3 and conc H2SO4 as a catalyst.
   - At 50 degrees celsius: electrophilic substitution.
2. Nitrobenzene to phenylamine:
   - Phenylamine is reacted with Tin(reducing agent), and conc HCl: reduction
   - The phenylammonium ion form is neutralised by NaOH to form phenylamine.

Question 11

How do you form a nitrile using haloalkanes?

Answer 11

A haloalkane is reacted with KCN in ETHANOL—> Nucleophilic substitution

Nucleophile: CN-
Substitutes the halogen with CN
:

R-X + KCN –> R-CN + X-